Audio VDt1
digital-to-analogue converter £3,650
exotica Longdog
Top dog
Longdog Audio’s VDt1 is a minimalist
high-end DAC with a difference, says
David Price, but is it the mutt’s nuts?
t
hese days, £3,500 gives
you a choice of a good
range of feature-laden
DACs and digital preamps.
Kitted out with fancy displays,
multifarious features and often with
streaming functionality too, they
seem to have more inputs than you’d
see in a recording studio desk. And
then there’s Longdog’s VDt1, which
is the diametrical opposite. The
objective of this stripped-down,
minimalist machine is – in the words
of designer Nick Gorham – to be a
digital convertor that “plays PCM as
well as it can”.
It also gives Direct Stream Digital
playback, too – DSD 64 only, 128 isn’t
supported. And so, at the Longdog’s
heart is a Japanese-sourced and
uncommon Asahi Kasei AK4396 DAC
chip, chosen because in Nick’s view it
was the best sounding around for his
intended application. It does the
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HFC_377_Exotica_Reprint.indd 42
digital filtering internally, with no
additional output filtering after the
analogue stage, other than that
provided by the output transformers.
Unusually, the analogue board
sports two JAN Philips 5687 triode
valves and because they are robust
and have very close matching
between them. They are very long life
tubes and to aid longevity there’s an
automatic standby feature, which
powers off the output stage after a
period of non-use. The system shuts
down the heater supply and HT for
the valves if it sees digital silence for
more than five minutes and turns
the normally blue power LED to a
flashing red colour; the DAC circuitry
is powered up all the time unless the
mains power is turned off at the back.
Three regulated power supplies are
provided, for the digital board main
supply, output stage valve heater
supply and valve-regulated high
DETAILS
PRODUCT
Longdog Audio VDt1
Origin
UK
Type
Digital-to-analogue
convertor
Weight
8kg
Dimensions
(WxHxD)
450 x 240 x 120mm
FEATURES
l 16 to 24-bit,
44.1kHz to 192kHz
PCM; DSD 64
playback
l Asahi Kasei
AK4396 DAC chip
l Tube output stage
with 2x Philips
5687s
l Galvanically
isolated inputs
DISTRIBUTOR
Mains Cables R Us
TELEPHONE
07908 056978
WEBSITE
mcru.co.uk
voltage supply using high voltage
MOSFETs and EF86 pentode. The
low noise HT supply ensures a low
analogue noise floor, Longdog says,
and the DAC itself is fed by two ultra
low noise voltage regulators. The
I2S and DSD inputs are isolated from
the receiver to avoid noise transfer
between stages. The digital board has
four stages of pre-regulation using
low-noise regulators, nine of which
are mounted beside the driven device.
The custom board design provides
isolated ground paths between stages,
and a toroidal transformer completes
the picture.
Real effort has been taken to
minimise the transmission of noise;
both from outside and that which is
generated inside. High-quality
socketry is apparent on the back
panel, and the digital inputs are
galvanically isolated with pulse
transformers – a great boon
considering the rubbish that can come
down a USB lead from a computer.
The S/PDIF receiver is supplied by
three separate ultra low noise voltage
regulators, the designer says, and
Tellurium Q Graphite USB cable is
used inside. Mechanical noise is
reduced by the solid casework that’s
supported by RDC cone feet, and the
casing and base is all aluminium to
avoid the generation of earth current
loops in the metalwork, both from
external fields and internally.
www.hifichoice.co.uk
17/9/13 09:36:18
exotica
Longdog Audio VDt1
digital-to-analogue converter £3,650
cannot always be completely sure
what you’ve actually got going out of
your computer! Still, it works well
as it is and doesn’t have a cluttered
fascia, which is no bad thing. A choice
of black or silver front panels is
offered, although the case remains
black whichever variant you specify.
The Longdog will work at the usual
16-bit/44.1kHz to 24-bit/192kHz
resolution; it will accept 32-bit
signals, but won’t process them. The
USB 2 interface requires no drivers
for Linux and Mac users, while there’s
a simple driver installation procedure
for Windows devotees. It supports
DSD over USB, 64-bit DSD and has
automatic switching between PCM
and DSD. Either of its two coaxial
digital input sockets can be
repurposed as Toslink or AES XLR
inputs to special order, or the RCA
audio outputs changed for XLRs.
With my MacBook Pro, the Longdog
hooks up with no messing, and works
seamlessly with my Audirvana Plus
hi-res software player; I also use an
Audiolab 8200CD CD player for
optical disc transport purposes.
enough to remind you that your
windows are made from breakable
glass. It’s a massive, gutsy sort of
sound that makes even dCS’ superb
high-end Debussy DAC look rather
over-polite. And the great thing is that
it’s not just big and punchy in a hi-fi
sort of way, it’s actually very naturally
musically satisfying, too.
Staying with 16-bit CD as a source,
and The Jam’s classic Down In a Tube
Station at Midnight thunders out.
Unlike so many
DACs it doesn’t
stand in the way of
the musical event
Sound quality
This DAC is well made; the
manufacturer has obviously taken
great care to produce a finely finished
product both inside and out. The
front panel knob selects between
three inputs (two coaxial and one
USB) and there’s a bank of handy
LEDs to indicate power, error
condition, DSD and HS Coax (which
lights when the coaxial input sees
88.2kHz sample rates or higher). I
would have liked to have seen an
additional way of displaying that
176.4kHz or higher has been
achieved too – and make this apply
to the USB input, just to make life
that little bit more certain. As any
computer audiophile knows, one
The stripped
down, minimalist
Longdog proves
that less is more
This is a warm, expansive performer
that will delight analogue addicts,
thanks to its particularly natural tonal
balance. Instead of a rather lean,
analytical, matter-of-fact sound that
you often get from digital-to-analogue
convertors, the Longdog gives a
smooth and sweet – if not quite
sumptuous – performance that makes
extended listening a pleasure. For
example, take Simple Minds’
Someone, Somewhere, In Summertime.
As well as being assaulted by a
grumbling bass line that’s as loud as
a forced realignment of the earth’s
tectonic plates, you’re assailed by a
metronomic, thumping snare and
hi-hat sound that feels positively
electric. It fizzes with energy, and
then the kick drum comes in loud
Although packed with amphetaminefuelled anger, it’s a pretty thin and
reedy-sounding recording and can
underwhelm, especially on CD, but
this DAC isn’t having that. Instead, it
serves up an engrossing sound that
gets me hooked. It perfectly catches
the expressive, plaintive tones of Paul
Weller’s vocals, and drives home
every last ounce of the song’s
powerful emotion. Unlike so many
DACs it simply doesn’t stand in the
way of the musical event. Indeed,
the VDt1 proves wonderfully subtle,
yet involving in its presentation;
vocals hover ethereally in a wide
soundstage, against a backdrop of
a powerful bass guitar, pushing the
song along.
So rather than treading the well
worn, respectable path of trying to
cover all the bases, it goes steaming
into the recording to see what it can
pull back out with breathtaking
energy. Digital geeks will know what
I’m talking about when I say that
it reminds me of the old Philips
TD1541-equipped eighties CD
players, which seemed to make every
piece of music you played on them
sound dramatic – epic, even. The
CONNECTIONS
1
5
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HFC_377_Exotica_Reprint.indd 43
2
4
1
IEC mains input
2
RCA analogue
output
3
Coaxial digital
input
4
USB digital input
5
Mains power
switch
3
Reprinted from
17/9/13 09:36:21
Audio VDt1
digital-to-analogue converter £3,650
exotica Longdog
Q&A
Nick Gorham
Designer Longdog Audio
In Sight
1
2
1
2
3
4
DP: How have you reduced noise
inside the DAC?
NG: I’ve used galvanic isolation. The
S/PDIF inputs are isolated by pulse
transformers from the rest of the DAC
circuit, so any earth current from the
source is prevented from entering
and potentially causing disruption,
noise and jitter. The USB input is not
directly isolated, but the USB
interface itself is isolated by the
addition of a high-speed isolator. The
analogue output of the DAC is again
isolated, to avoid the potential to set
up ground loops between the DAC
and the equipment it is driving. In this
case the isolation is provided by the
nickel core output transformers in the
DAC. Also within the DAC itself, a
isolator is used between the receiver
section and the DAC section.
Why did you choose to use tubes in
the output stage?
In my view they offer the best
solution to taking the signal directly
from the DAC output and presenting
it to the following equipment. The
output stage presents a very high
impedance load to the DAC output,
and could be considered as a 1.5W
push pull tube power amplifier. Unlike
most tube output stages used in DAC
designs, this stage is not intended to
add its own character to the sound,
the fully balanced transformercoupled design would be familiar to
any engineer used to working on
sixties’ studio tube equipment. In
terms of measurement, the output
stage produces similar numbers to
conventional op-amp based output
stages, so nothing is lost, but the
clarity and lack of higher order
distortion products means that the
goal of offering the best of both
worlds is attained.
Why have DSD on a DAC?
Simply choice. Some material is
available as PCM and some as DSD,
there are no additional parts required
in the signal chain to offer the option,
so it seemed obvious to offer the
feature. Now that streaming is the
source of choice for many, and USB
offers the option of encoding DSD
within a standard 24-bit packet it’ll be
interesting to see what listeners pick.
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HFC_377_Exotica_Reprint.indd 44
5
5
HOW it
COMPARES
Costing £4,100 with
AES/EBU, RCA, BNC
and optical inputs – plus
USB – the Astin Trew
Concord 1 is the closest
competitor. And with
a high-quality tube
output stage – in this
case it is switchable and
you can use the solidstate one – it is quite
similar in concept. It is
based around two Burr
Brown PCM1794 DAC
chips running in dual
mono configuration, so
there’s a different chip
at its heart. The Astin
Trew sounds superb,
but is a fractionally
brighter and lighter
sounding device than
the Longdog. Not that
the latter is fat and
overly rich, but it is a
little deeper and more
three dimensional. Both
are very fine machines,
and not dissimilar in
terms of the end result.
4
VDt1, of course, has more refinement
and depth than such players, but still
goes about the job of making music in
much the same sort of fashion.
Feed it some hi-res music via its USB
input and it really begins to shine.
Art of Noise’s Moments in Love at
24/88.2 is just superb, the DAC
capturing the synthesised rhythm
backing beautifully, giving a very
realistic sense of texture. At the same
time, those big synth stabs sound
powerful and menacing, and backing
vocals creamily smooth. The Longdog
sets up a spacious soundstage, one
that hangs back well, but projects
powerfully into the room, too.
Everything seems to syncopate so
convincingly; sparse electronic music
such as this relies on the rhythmic
interplay between instruments for
effect, and in this case it proves the
DAC’s fine timing. For me, the ability
to combine believable tonality with
fine timing isn’t universal in a DAC of
any price, let alone this, so the VDt1
is in good company.
Firing up some high-powered thrash
metal courtesy of Metallica’s Enter
Sandman at 24/96, shows that it can
rock out with the best of them. This is
a true large-stage production, one
with all the faders set to eleven, and
the Longdog shows this in no
uncertain terms. Bass is deep and
powerful in a way that few similarly
priced designs are. In absolute terms
it’s a fraction on the warm side, with
a slight extra weight in the upper
bass, but it lacks the instantaneous
start-stop of the very highest-end
solid-state DACs. Midband is very
detailed and drops back surprisingly
far, giving an enjoyable immersive
sort of feel, and the treble is sweet
Nickel core output
transformers
Regulated high
voltage power
supply
Oversize, low hum
field toroidal mains
transformer
Standby power
supply
Philips 5687 triode,
balanced valve
output stage
3
and smooth – again some will
bemoan a slight lack of bite, while
others will love it. The same goes for
a DSD file of Alex de Grassi’s The
Water Garden, which has a lovely
lilting sound. Again, a naturally open,
smooth and enthusiastic nature
shines through, and it serves up a
highly involved rendition of the
music, with lots of detail and focus.
Conclusion
Here’s an interesting new DAC that
can hold its head high even among
considerably more expensive types in
terms of pure sonics. It isn’t quite as
swish looking as some price rivals,
because much of the budget has gone
towards getting it to sound superb –
and it’s been money well spent. If
you’re looking for a minimalist,
high-performance digital convertor,
then the Longdog VDt1 illustrates
how less can be more! If you take
your digital and/or computer audio
seriously, but aren’t too concerned
about a vast range of features, it’s an
essential audition l
Our verdict
SOUND QUALITY
VALUE FOR MONEY
Build Quality
features
LIKE: Very natural,
musical, organic sound
with power and punch
DISLIKE: It could do
with a sampling rate
display and some
more inputs
WE SAY: Singleminded audiophile
product purposed for
top performance
OVERALL
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17/9/13 09:36:26